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# Need help with a trig question watch

1. Can anyone pls explain how to do this question. I tried to do it using the circle but it is not right and it would be great if u could also explain how to use the graph to solve this. I am stuck because I thinkat the end you divide all the solution by 2 then -15 right? Thanks
2. Anyone???
3. (Original post by coconut64)
Can anyone pls explain how to do this question. I tried to do it using the circle but it is not right and it would be great if u could also explain how to use the graph to solve this. I am stuck because I thinkat the end you divide all the solution by 2 then -15 right? Thanks
Your working looks correct so far. Just remember there will be a few results.
4. Isn't the range meant to be 15<=2x+15<=735
5. (Original post by Albus Hagrid)
Isn't the range meant to be 15<=2x+15<=735
My teacher told me to do that right at the end so you would get your solution, divide it by 2 then minus 15. But my answers are wrong...
6. (Original post by Andy98)
Your working looks correct so far. Just remember there will be a few results.
So the first solution I got is 64.63 and I divided it by 2 and -15 but when I sub it in it doesn't equal to 2....
7. (Original post by coconut64)
My teacher told me to do that right at the end so you would get your solution, divide it by 2 then minus 15. But my answers are wrong...
for

Let

Solve for

What do you get for those stages?
8. (Original post by Andy98)
for

Let

Solve for

What do you get for those stages?
Thanks so much! I got it now, so does 2x+15 or whatever inside the bracket represent theta?
9. (Original post by coconut64)
Thanks so much! I got it now, so does 2x+15 or whatever inside the bracket represent theta?
Yes.
10. (Original post by Andy98)
Yes.
Thanks. I appreciate the help
11. (Original post by coconut64)
Thanks. I appreciate the help
No problem
12. (Original post by Andy98)
No problem
Hi again, if you have yo solve sin^2x=1, do you factorise it or square root it? Thanks
13. Hey. I got 4 solutions? 294.1, 204.2, 114.2 and 24.2. I may be wrong, I haven't done this since my exams lool
I believe this is CAST and there is a waaay easier method, my teacher always is like "any teacher who teaches cast is ****" LOL but it's called General Solutions; if you want I can teach you it.
14. There's actually no need to use CAST diagrams; I never did. There's a much, much quicker way.
15. (Original post by coconut64)
Hi again, if you have yo solve sin^2x=1, do you factorise it or square root it? Thanks
Well you should see quite easily that sinx = ±1.
16. (Original post by PrimeLime)
There's actually no need to use CAST diagrams; I never did. There's a much, much quicker way.
Nor did I - never really grasped how they worked tbh

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17. (Original post by Andy98)
Nor did I - never really grasped how they worked tbh

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Did you just do what I do: 180-solution for sine, 360-solution for cos etc.?
18. (Original post by PrimeLime)
Did you just do what I do: 180-solution for sine, 360-solution for cos etc.?
Yeah

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19. (Original post by Michaelj99)
Hey. I got 4 solutions? 294.1, 204.2, 114.2 and 24.2. I may be wrong, I haven't done this since my exams lool
I believe this is CAST and there is a waaay easier method, my teacher always is like "any teacher who teaches cast is ****" LOL but it's called General Solutions; if you want I can teach you it.
20. (Original post by coconut64)
I don't know whether you should learn this method. It'll likely make you forget how trig equations work.

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Updated: November 8, 2015
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